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Energy expenditure and heart rate response to breaking up sedentary time with three different physical activity interventions
Nutrition, Metabolism & Cardiovascular Diseases (2015) 25, 503e509
Available online at www.sciencedirect.com
Nutrition, Metabolism & Cardiovascular Diseases journal homepage: www.elsevier.com/locate/nmcd
Energy expenditure and heart rate response to breaking up sedentary time with three different physical activity interventions S.E. Carter*, M. Jones, V.F. Gladwell Centre for Sports and Exercise Science, Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, United Kingdom Received 11 November 2014; received in revised form 13 February 2015; accepted 16 February 2015 Available online 24 February 2015
KEYWORDS Sedentary behaviour; Workplace; Calisthenics; Energy expenditure; Heart rate
Abstract Background and aims: Prolonged sedentary behaviour is associated with increased cardiovascular disease risk and decreased energy expenditure (EE). Workplace interventions breaking up sedentary time have increased EE but the cardiovascular responses are unknown. The practicalities of these interventions, such as required costs and workplace adaptations, are questioned. Calisthenics exercises overcome such limitations, but have not been assessed. The aim of this study was to assess the EE and heart rate (HR) response when breaking up sedentary time with a short bout of standing, walking or calisthenics. Methods and results: Twenty healthy participants (15 male) completed four 30 min conditions: a) 30 min sitting, or breaking up this period with two minutes of b) standing, c) treadmill walking (4 km$h1) or d) a set of calisthenics exercises (including squats and lunges). HR and EE (indirect calorimetry) were assessed throughout. During the activity break, calisthenics caused the highest HR (90 12 bpm) compared to all other conditions (Sit: 70 12 bpm; Stand:72 13 bpm; Walk:84 10 bpm; p < 0.001) and EE was the highest with calisthenics (13 5 kcal) compared to all conditions except walking (Sit:3 1 kcal; Stand:5 1 kcal; p < 0.001). The recovery following calisthenics had highest total EE (27 7 kcal) compared to walking (23 6 kcal) and standing (22 6 kcal) and also the longest elevation of HR (p < 0.001). Conclusion: Calisthenics led to a greater total EE and HR response compared to standing or walking interventions. Calisthenics may be a time efficient method to break up sedentary time without individuals leaving their work environment. Hence calisthenics could be utilised to disrupt workplace sedentary time and improve cardiovascular health and assist in weight management. ª 2015 Elsevier B.V. All rights reserved.
Introduction Time spent sedentary is increasing both in the workplace and during everyday life [1,2]. Physical inactivity has long been recognised as detrimental for cardiovascular and metabolic health [3] however, emerging research has
* Corresponding author. Present address: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, L3 3AF, United Kingdom. Tel.: þ44 07708226464. E-mail address: [email protected] (S.E. Carter). http://dx.doi.org/10.1016/j.numecd.2015.02.006 0939-4753/ª 2015 Elsevier B.V. All rights reserved.
identified sedentary behaviour as an independent health risk factor [2,4]. Prolonged sitting is associated with decreased metabolic health [1,5], cardiovascular disease [1,5,6] and increased mortality [1,2,7]. Moreover, low energy expenditure (EE) with sitting [3] is implicated in the increased prevalence of overweight and obesity [8,9], making sedentary behaviour an expanding research area within physical activity and health [2]. In a work-based environment, standing increases EE [10]. However, prolonged standing may induce lower extremity swelling, venous pooling, lower limb fatigue and
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lower back pain [11], thus longer term energy balance improvements could be negated by health complications. Alternatively, short bouts of physical activity can be used to interrupt sedentary time. One, two and five minute self-selected speed corridor walks elevated gross EE by 3.2 kcal$30 min1, 7.6 kcalv30 min1, 16.6 kcal$30 min1 respectively compared to 30 min sitting [12]. Extrapolating these results for a day, week or month, potentially leads to important increases in EE [12]. Additionally, compared to remaining seated for five hours, light and moderate intensity walking breaks every 20 min lowered resting blood pressure, however no differences were observed in heart rate (HR) [13]. Importantly, the HR responses during and immediately after the activity bouts were not measured, which can provide important information about the intensity of activity, the recovery of the cardiovascular system and may explain changes in EE. Free walking however cannot be undertaken in all workplaces and treadmill desks are an alternative option [10]. Compared to standard desks, obese individuals walking and working for one hour increased their EE by 119 kcal$h1 [8]; while in the long term overweight and obese individuals had improved body composition [14], waist and hip circumference, low-density lipoproteins and total cholesterol [9]. Treadmill desks may not interfere with workplace activities [15] but their cost may limit practical application [16] especially for an entire workforce. Calisthenics exercises, such as body weight squats and lunges, overcome many of the limitations associated with office walking and treadmill desks. Exercises could be easily performed in small spaces, without equipment. Furthermore, calisthenics can target other fitness components, such as muscular strength, coordination, flexibility and balance, which are specified in current adult physical activity guidelines [17,18]. The use of calisthenics to break up sedentary time has not been studied; therefore any potential changes in EE are unknown. The purpose of this study was to determine and compare the EE and HR response to breaking up sedentary time with a short bout of standing, walking or calisthenics. This would determine if calisthenics could potentially be utilised as an intervention to break up sedentary behaviour and assist in weight management.
S.E. Carter et al.
Methods Study population Twenty healthy participants (15 male) completed the study (Mean SD, age: 24.0 6.1 years, body mass: 75.2 17.5 kg, height: 172.8 10.7 cm, body mass index: 25.0 4.2 kg/m2). Participants were screened prior to testing (PAR-Q) and exclusion criteria included: smoking, current medication and presence of apparent cardiovascular or metabolic disease. Study design and procedures A within-subjects design was followed. On a single occasion participants attended the temperature controlled (20e22 C) laboratory. Prior to testing participants were instructed to avoid strenuous exercise for 48 h and any exercise for 12 h prior, to avoid consuming caffeine or other stimulants 24 h prior and not to consume food 4 h before testing. Following instrumentation with a HR monitor and face mask for gas collection, participants rested in a seated position for 10 min. Subsequently, in a set order four consecutive 30 min conditions were completed, each separated with a 5 min recovery period. In condition one, participants remained seated at a desk for 30 min. The further three conditions involved breaking up this sedentary time with 2 min of either: a) standing, b) low intensity walking, or c) low intensity calisthenics exercises. For each condition the same time course was followed: participants sat for 13 min, performed the physical activity intervention for 2 min and then returned to sitting for a further 15 min. To ensure a consistent physical activity time across conditions and participants, a standardised transition time between sitting to starting each intervention and then returning to sitting afterwards was included lasting 25 and 15 s respectively. Each condition was therefore broken down into five separate periods (Fig. 1). Condition 1: sitting and other sedentary periods During all sedentary periods participants remained seated in a chair at a desk and were permitted to read, work on a computer or perform other desk-based activities.
Figure 1 Experimental design for the four conditions conducted in a single 2 h laboratory session: (a) Sitting for 30 min or (b) breaking up this period with 2 min of: standing stationary, treadmill walking or calisthenics exercises.
Energy expenditure and heart rate response
Condition 2: standing Participants stood unassisted behind their chair, with as little postural sway as possible. Condition 3: walking Walking was performed on a treadmill (GX200 Powerjog, Sport Engineering Ltd, Bimingham, UK) at a set speed of 4 km$h1. Speed was selected based on previous research in which participants’ self-selected pace for a 2 min corridor walk was 64.2 m$min1, thereby equalling 3.9 km$h1 [12]. Condition 4: calisthenics exercises Five consecutive exercises were performed in a set order of: squats, arm circles, calf raises, knees to elbows and lunges. Using a combined audible and visual metronome, participants performed 8 repetitions of each exercise across a 3 s cycle, totalling 24 s per exercise. Prior to testing participants were provided with this information alongside instructions as to each exercise technique and additional demonstration was provided on the test day.
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from pre-intervention between the four conditions. Additionally, for HR recovery analysis two-way repeated measures ANOVA with “condition” and “time” treated as within subject variables was used to compare HR at baseline (sit period 1), 60, 120, 180, 240 and 300 s following the intervention between the standing, walking and calisthenics conditions, while a priori comparisons were made between baseline and all other time points. All post hoc analyses were performed via paired samples ttest with Bonferroni adjustment. Data was analysed using statistical software (SPSS Version 18.0, IBM Corporation, Somers, NY, USA), with significance accepted as p 0.05. Ethics statement Experimental procedures and potential risks were explained to participants prior to testing and written informed consent obtained. The University of Essex ethics committee approved the experimental protocol, which conformed to the Declaration of Helsinki. Results
Experimental measures Energy expenditure During each condition, breath by breath oxygen consumption (VO2) and carbon dioxide production (VCO2) were measured and respiratory exchange ratio (RER) calculated at 5 s intervals via indirect calorimetry (CPX, Jaeger, Hoechberg, Germany). HR was also continually monitored (S610i, Polar Electro Oy, Kempele, Finland) with measures taken at 5 s intervals. Energy expenditure calculations EE was calculated using the Weir equation: kcal$min1 Z [(1.1 RER) þ 3.9] VO2 L$min1 [19]. For each condition, one minute averages of VO2 and RER were used to determine EE per minute of assessment. Values were then summed to give the total EE for the entire condition. Additionally, the standing, walking and calisthenics conditions were broken down into their five periods (Fig. 1) and the EE determined. Heart rate analysis For each condition average HR for the entire assessment period was determined and also broken down into the five periods (Fig.1). Average HR and %HRmax ((bpm) Z 220 age) was calculated to compare intensity of exercise. HR recovery in the five minutes following each intervention was assessed by determining the mean HR at each minute. Statistical analysis All data are presented as mean SD. Data were normally distributed, assessed using KolmogoroveSmirnov test. Repeated measures analysis of variance (ANOVA) was used to compare: total EE, intervention EE, pre-intervention EE, post-intervention EE, intervention HR and change in HR
Total EE differed between the four conditions (F(3,57) Z 75.0, p < 0.001) (Fig. 2(a)), with calisthenics causing the largest increase (57 16 kcal) compared to all other conditions (Sit: 42 11 kcal, p < 0.001; Stand: 44 12 kcal, p < 0.001; Walk: 52 13 kcal, p < 0.001). Pre-intervention EE was not different between interventions (Stand: 18 5 kcal; Walk: 19 5 kcal; Calisthenics: 19 5 kcal; F(3,57) Z 0.4, p Z 0.8) or sitting (19 5 kcal, p Z 0.8) indicating participants had sufficiently recovered between conditions. Considering the intervention period in isolation (transition 1, intervention period and transition 2) calisthenics resulted in the highest EE (13 5 kcal) (Fig. 2b) compared to sitting (3 1 kcal, p < 0.001) and standing (5 1 kcal, p < 0.001). Recovery EE following the intervention differed between conditions (F(3,57) Z 47.5, p < 0.001) (Fig. 2c) with calisthenics resulting in the highest total EE (27 7 kcal) compared to both walking (23 6 kcal, p < 0.001) and standing (22 6 kcal, p < 0.001). Compared to sitting for 30 min, an additional 6.5% or 3 kilocalories were expended by breaking this period up with 2 min of standing; 24.9% or 10 additional kilocalories were expended walking for 2 min; and 37.8% or 16 additional kilocalories were expended performing 2 min of calisthenics. Larger expenditures would be gained if these interventions were performed over the longer term, assuming energy intake is maintained (Table 1). Exercise intensity All conditions were classified as ‘very light’ intensity (<57 %HRmax) in accordance to the American College of Sports Medicine (ACSM) exercise prescription guidelines [18] (Sit:
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36 6%; Stand: 37 6%; Walk: 43 5%; Calisthenics: 46 6%). Heart rate response The HR response to the intervention differed between conditions (F(3,57) Z 53.5, p < 0.001). Calisthenics (90 12 bpm) and walking (84 10 bpm) HRs were higher compared to sitting (70 12 bpm, both p Z 0.001). Moreover, calisthenics resulted in the highest HR (25 6 bpm) from pre-intervention values compared to walking (17 5 bpm, p < 0.001) and standing (8 5 bpm, p < 0.001). For recovery HR (five minutes following intervention), a significant interaction between condition and time was observed (F(10,150) Z 22.8, p < 0.001) (Fig. 3). Following calisthenics, HR was elevated above baseline at 60 and 120 s into the recovery (p < 0.001), with increases of 12 bpm and 5 bpm respectively. This did not return to near pre-intervention values until 180 s onwards. In contrast following walking, HR remained above baseline for 60 s into the recovery (p < 0.001), with a 4 bpm increase, but returned toward baseline by 120 s. Standing values recovered within the first minute. Discussion
Figure 2 Differences in energy expenditure when completing 30 min sitting (Sit) or breaking up this period with a two minute intervention of: standing stationary (Stand), treadmill walking (Walk) or performing calisthenics exercises (Calisthenics). (2a) Total energy expenditure during the 30 min assessment period. (2b) Energy expenditure during two minutes of sitting and during each two minute intervention. (2c) Energy expenditure during 15 min of sitting and in the 15 min sitting period following each intervention. * Significantly greater than sit (p < 0.001), # significantly greater than stand (p < 0.001), ** significantly greater than walk (p < 0.001). (Error bars Z SD).
This study investigated calisthenics as an alternative intervention choice which could be utilised to interrupt sedentary time. A two minute set of calisthenics as a break during 30 min of sitting, led to a greater total EE and HR response compared to standing or walking for the same time period. Additionally, calisthenics could be performed behind a desk with no additional equipment, increasing the potential practical application in workplaces. Hence, this study presents calisthenics as a potentially more time efficient intervention to break up sedentary behaviour which could be utilised to improve cardiovascular health and weight management. Interrupting sedentary time with calisthenics produced the greatest total EE; higher than standing or walking. The EE for a given activity is determined by the volume of contracting muscle mass [20] and, compared to sitting, standing and walking leads to elevated contractile activity [3,21]. Moreover, quadriceps and hamstring muscle activity is greater when squatting than standing or brisk walking [21]; consequently the muscle activity required to perform the calisthenics would also produce an increased EE. Performing fidgeting-like movements also increases EE compared to remaining motionless [22], demonstrating activating even small musculature can heighten EE. The nature of the calisthenics completed challenged fitness components such as balance and coordination which in turn may have activated a greater number of smaller muscle fibres, such as limb stabilising muscles, as well as larger trunk muscles. It could therefore be possible that this greater overall muscle contractile activity could
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Table 1 Extrapolation of the additional energy expended (compared to sitting) when disrupting 30 min of sitting with 2 min of standing, walking or calisthenics exercises. Time period
1h 8 h working day 5 days of 8 h working days 1 month of 8 h working days 6 months of 8 h working days 12 months of 8 h working days
Energy expenditure (kcal) 2 min of standing once every hour
2 min of walking once every hour
2 min of calisthenics exercises once every hour
3 24 108 432 2592 5184
10 80 412 1648 9888 19,776
16 128 628 2512 15,072 30,144
Note: Once every hour has been selected to best represent a realistic working day, taking into account the possibility of daily events (such as meetings) which may prevent more frequent breaks in sedentary time. Values have been rounded whole numbers.
Figure 3 Mean heart rate at baseline (15 min sitting) and during five minutes of recovery following breaking up this sedentary period with two minutes of: standing stationary (Stand), treadmill walking (Walk) or performing calisthenics exercises (Calisthenics) (shaded area). * indicates calisthenics caused a significantly greater heart rate than baseline (p < 0.001). # indicates walking caused a significantly greater heart rate than baseline (p < 0.001). (Error bars Z SD).
explain the larger EE observed. Additionally, during the recovery following the intervention calisthenics produced a longer elevation of EE and also HR compared to the other conditions. Excess post-exercise oxygen consumption (EPOC) occurs during the recovery following physical activity and a component of this is the increased cardiac response [23]. Consequently, the longer elevation of HR following calisthenics might provide a mechanism to explain the concurrent increased EE observed. Practical applications Using calisthenics as an intervention to break up sedentary time is a more time efficient one than the other methods assessed. Performing calisthenics led to a 37.8% increase (16 kcal) in total EE compared to sitting, whereas walking and standing led to only 24.9% (10 kcal) and 6.5% (3 kcal) increases respectively. Furthermore, previous interventions employed to elevate EE have not achieved such substantial calorific increases. Breaking up sitting desk work with a two minute self-paced walk led to only a 17% increase in EE (8 kcal)
[12]. Only when this intervention was carried out for five minutes did EE nearly match that achieved from the calisthenics in this study, with a 37% increase (17 kcal) observed [12]. Therefore calisthenics can provide the same EE benefits as walking but in less than half the time. Similarly if standing is employed as opposed to sitting, an energy expenditure of 1.37 kcal$min1 [8] has been reported, but this is less than the 1.91 kcal$min1 expended performing calisthenics as an intervention. Moreover, in this study [8] standing was utilised for the entire assessment duration rather than as a break, causing the time length of the meaningful intervention to be considerably longer than a two minute set of calisthenics. In practical terms the time efficiency of calisthenics is of great significance as individuals may lack the opportunity during a workday to spend such considerable time away from their working environment, or may not have access to suitable facilities to stand and work. Calisthenics may also represent a more feasible option to apply to workplaces. The calisthenics routine prescribed overcomes previous limitations, such as equipment costs and workplace restrictions, as it could be easily performed behind a desk, in a small amount of space and with no equipment required. Additionally, based on the HR response, the intensity of the calisthenics routine was only ‘very light’ [18] meaning workers could return to their desk immediately afterwards without feelings of excessive exertion. Longer term benefits Although this was an acute study, the responses observed breaking up sedentary time with a single bout of calisthenics have the potential to produce longer term health benefits if this routine was performed over an extended time period. Employing calisthenics every hour over an eight hour working day, an additional 128 kcal would be expended, well above the daily 100 kcal threshold suggested to reduce weight gain [24]. Extrapolating the EE when walking or standing for a working day, values fail to reach the target 100 kcal a day value [24]. Additionally, potentially larger expenditures could be gained performing calisthenics over an extended time period (Table 1). However, this positive
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Conclusion
change in EE resulting from calisthenics is dependent on whether there is no compensatory increase in energy intake as a result of the increased physical activity [25]. The repeated performance of the calisthenics employed in this study has the potential to maintain or improve additional fitness components such as muscular strength, flexibility and balance, which are specified in current adult physical activity guidelines [17,18]. These core fitness components are essential to everyday functional activities and can deteriorate with age and physical inactivity [26]. It is unknown if longer term cardiovascular or metabolic adaptations could occur performing the calisthenics. The elevation in HR and subsequently blood flow and shear stress has the potential to provide benefits to the vasculature, specifically endothelial function, a measure of cardiovascular health associated with cardiovascular risk [27]. Additionally, the potential of increased muscle mass and subsequent glucose transporter protein content would enhance glucose uptake, improving insulin sensitivity [28].
This study demonstrates calisthenics are a time efficient method to break up sedentary time, which has the practical potential to be employed in workplaces. Calisthenics led to a greater total EE and HR response compared to using standing or walking as an intervention, which in the long term may assist in weight control. This exercise modality also targets fitness components such as muscular strength, balance and co-ordination, which are features of physical activity guidelines. Furthermore, performing calisthenics does not require individuals to leave their desk environment or purchase additional equipment, thus overcoming previous limitations associated with other workplace interventions. Although longer term research is required to assess the feasibility of this intervention, this study presents calisthenics as a promising alternative to break up prolonged workplace sedentary time and improve cardiovascular health and assist in weight maintenance.
Limitations and future research
Acknowledgements
The design of this study was not counterbalanced, therefore it is possible the order of the conditions may have influenced results. To reduce this, a five minute recovery between conditions was included. No differences between conditions in EE or HR prior to each intervention were observed, indicating participants had recovered from the previous condition. The calisthenics intervention utilised only five different calisthenic exercises, selected to target a combination of fitness components. However, utilising different combinations and types of exercises may in turn influence the magnitude of the EE and HR response. Consequently, additional research utilising varied exercises is required. Although performing calisthenics resulted in the highest EE and HR responses, it is acknowledged that following this protocol over an eight hour working day may be too intensive for some individuals. For example over one day an individual repeating this routine would perform 64 repetitions of each exercise, which may be excessive for those without previous experience of these exercise modalities, and this would be further exacerbated over an entire working week. Moreover, this routine utilised only five different types of calisthenics, hence over time their repeated performance could become demotivating, leading to decreased adherence. Additionally, results cannot be generalised to the entire population as the magnitude of change in EE could have been influenced by factors such as body weight [29] and fitness levels [30]. Longer term studies are therefore needed assessing the calisthenics routine over several days to determine the feasibility of individuals carrying out multiple repetitions of the exercises (including changes in work productivity), alongside any potential health complications that may result such as muscle soreness or injury. It may be that a combined approach with walking (or other activities) may be more suitable to interrupt sedentary time. Furthermore this exercise variety could increase adherence, which can be problematic with lifestyle modifications [31].
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Energy expenditure and heart rate response to breaking up sedentary time with three different physical activity interventions S.E. Carter*, M. Jones, V.F. Gladwell Centre for Sports and Exercise Science, Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, United Kingdom Received 11 November 2014; received in revised form 13 February 2015; accepted 16 February 2015 Available online 24 February 2015
KEYWORDS Sedentary behaviour; Workplace; Calisthenics; Energy expenditure; Heart rate
Abstract Background and aims: Prolonged sedentary behaviour is associated with increased cardiovascular disease risk and decreased energy expenditure (EE). Workplace interventions breaking up sedentary time have increased EE but the cardiovascular responses are unknown. The practicalities of these interventions, such as required costs and workplace adaptations, are questioned. Calisthenics exercises overcome such limitations, but have not been assessed. The aim of this study was to assess the EE and heart rate (HR) response when breaking up sedentary time with a short bout of standing, walking or calisthenics. Methods and results: Twenty healthy participants (15 male) completed four 30 min conditions: a) 30 min sitting, or breaking up this period with two minutes of b) standing, c) treadmill walking (4 km$h1) or d) a set of calisthenics exercises (including squats and lunges). HR and EE (indirect calorimetry) were assessed throughout. During the activity break, calisthenics caused the highest HR (90 12 bpm) compared to all other conditions (Sit: 70 12 bpm; Stand:72 13 bpm; Walk:84 10 bpm; p < 0.001) and EE was the highest with calisthenics (13 5 kcal) compared to all conditions except walking (Sit:3 1 kcal; Stand:5 1 kcal; p < 0.001). The recovery following calisthenics had highest total EE (27 7 kcal) compared to walking (23 6 kcal) and standing (22 6 kcal) and also the longest elevation of HR (p < 0.001). Conclusion: Calisthenics led to a greater total EE and HR response compared to standing or walking interventions. Calisthenics may be a time efficient method to break up sedentary time without individuals leaving their work environment. Hence calisthenics could be utilised to disrupt workplace sedentary time and improve cardiovascular health and assist in weight management. ª 2015 Elsevier B.V. All rights reserved.
Introduction Time spent sedentary is increasing both in the workplace and during everyday life [1,2]. Physical inactivity has long been recognised as detrimental for cardiovascular and metabolic health [3] however, emerging research has
* Corresponding author. Present address: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, L3 3AF, United Kingdom. Tel.: þ44 07708226464. E-mail address: [email protected] (S.E. Carter). http://dx.doi.org/10.1016/j.numecd.2015.02.006 0939-4753/ª 2015 Elsevier B.V. All rights reserved.
identified sedentary behaviour as an independent health risk factor [2,4]. Prolonged sitting is associated with decreased metabolic health [1,5], cardiovascular disease [1,5,6] and increased mortality [1,2,7]. Moreover, low energy expenditure (EE) with sitting [3] is implicated in the increased prevalence of overweight and obesity [8,9], making sedentary behaviour an expanding research area within physical activity and health [2]. In a work-based environment, standing increases EE [10]. However, prolonged standing may induce lower extremity swelling, venous pooling, lower limb fatigue and
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lower back pain [11], thus longer term energy balance improvements could be negated by health complications. Alternatively, short bouts of physical activity can be used to interrupt sedentary time. One, two and five minute self-selected speed corridor walks elevated gross EE by 3.2 kcal$30 min1, 7.6 kcalv30 min1, 16.6 kcal$30 min1 respectively compared to 30 min sitting [12]. Extrapolating these results for a day, week or month, potentially leads to important increases in EE [12]. Additionally, compared to remaining seated for five hours, light and moderate intensity walking breaks every 20 min lowered resting blood pressure, however no differences were observed in heart rate (HR) [13]. Importantly, the HR responses during and immediately after the activity bouts were not measured, which can provide important information about the intensity of activity, the recovery of the cardiovascular system and may explain changes in EE. Free walking however cannot be undertaken in all workplaces and treadmill desks are an alternative option [10]. Compared to standard desks, obese individuals walking and working for one hour increased their EE by 119 kcal$h1 [8]; while in the long term overweight and obese individuals had improved body composition [14], waist and hip circumference, low-density lipoproteins and total cholesterol [9]. Treadmill desks may not interfere with workplace activities [15] but their cost may limit practical application [16] especially for an entire workforce. Calisthenics exercises, such as body weight squats and lunges, overcome many of the limitations associated with office walking and treadmill desks. Exercises could be easily performed in small spaces, without equipment. Furthermore, calisthenics can target other fitness components, such as muscular strength, coordination, flexibility and balance, which are specified in current adult physical activity guidelines [17,18]. The use of calisthenics to break up sedentary time has not been studied; therefore any potential changes in EE are unknown. The purpose of this study was to determine and compare the EE and HR response to breaking up sedentary time with a short bout of standing, walking or calisthenics. This would determine if calisthenics could potentially be utilised as an intervention to break up sedentary behaviour and assist in weight management.
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Methods Study population Twenty healthy participants (15 male) completed the study (Mean SD, age: 24.0 6.1 years, body mass: 75.2 17.5 kg, height: 172.8 10.7 cm, body mass index: 25.0 4.2 kg/m2). Participants were screened prior to testing (PAR-Q) and exclusion criteria included: smoking, current medication and presence of apparent cardiovascular or metabolic disease. Study design and procedures A within-subjects design was followed. On a single occasion participants attended the temperature controlled (20e22 C) laboratory. Prior to testing participants were instructed to avoid strenuous exercise for 48 h and any exercise for 12 h prior, to avoid consuming caffeine or other stimulants 24 h prior and not to consume food 4 h before testing. Following instrumentation with a HR monitor and face mask for gas collection, participants rested in a seated position for 10 min. Subsequently, in a set order four consecutive 30 min conditions were completed, each separated with a 5 min recovery period. In condition one, participants remained seated at a desk for 30 min. The further three conditions involved breaking up this sedentary time with 2 min of either: a) standing, b) low intensity walking, or c) low intensity calisthenics exercises. For each condition the same time course was followed: participants sat for 13 min, performed the physical activity intervention for 2 min and then returned to sitting for a further 15 min. To ensure a consistent physical activity time across conditions and participants, a standardised transition time between sitting to starting each intervention and then returning to sitting afterwards was included lasting 25 and 15 s respectively. Each condition was therefore broken down into five separate periods (Fig. 1). Condition 1: sitting and other sedentary periods During all sedentary periods participants remained seated in a chair at a desk and were permitted to read, work on a computer or perform other desk-based activities.
Figure 1 Experimental design for the four conditions conducted in a single 2 h laboratory session: (a) Sitting for 30 min or (b) breaking up this period with 2 min of: standing stationary, treadmill walking or calisthenics exercises.
Energy expenditure and heart rate response
Condition 2: standing Participants stood unassisted behind their chair, with as little postural sway as possible. Condition 3: walking Walking was performed on a treadmill (GX200 Powerjog, Sport Engineering Ltd, Bimingham, UK) at a set speed of 4 km$h1. Speed was selected based on previous research in which participants’ self-selected pace for a 2 min corridor walk was 64.2 m$min1, thereby equalling 3.9 km$h1 [12]. Condition 4: calisthenics exercises Five consecutive exercises were performed in a set order of: squats, arm circles, calf raises, knees to elbows and lunges. Using a combined audible and visual metronome, participants performed 8 repetitions of each exercise across a 3 s cycle, totalling 24 s per exercise. Prior to testing participants were provided with this information alongside instructions as to each exercise technique and additional demonstration was provided on the test day.
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from pre-intervention between the four conditions. Additionally, for HR recovery analysis two-way repeated measures ANOVA with “condition” and “time” treated as within subject variables was used to compare HR at baseline (sit period 1), 60, 120, 180, 240 and 300 s following the intervention between the standing, walking and calisthenics conditions, while a priori comparisons were made between baseline and all other time points. All post hoc analyses were performed via paired samples ttest with Bonferroni adjustment. Data was analysed using statistical software (SPSS Version 18.0, IBM Corporation, Somers, NY, USA), with significance accepted as p 0.05. Ethics statement Experimental procedures and potential risks were explained to participants prior to testing and written informed consent obtained. The University of Essex ethics committee approved the experimental protocol, which conformed to the Declaration of Helsinki. Results
Experimental measures Energy expenditure During each condition, breath by breath oxygen consumption (VO2) and carbon dioxide production (VCO2) were measured and respiratory exchange ratio (RER) calculated at 5 s intervals via indirect calorimetry (CPX, Jaeger, Hoechberg, Germany). HR was also continually monitored (S610i, Polar Electro Oy, Kempele, Finland) with measures taken at 5 s intervals. Energy expenditure calculations EE was calculated using the Weir equation: kcal$min1 Z [(1.1 RER) þ 3.9] VO2 L$min1 [19]. For each condition, one minute averages of VO2 and RER were used to determine EE per minute of assessment. Values were then summed to give the total EE for the entire condition. Additionally, the standing, walking and calisthenics conditions were broken down into their five periods (Fig. 1) and the EE determined. Heart rate analysis For each condition average HR for the entire assessment period was determined and also broken down into the five periods (Fig.1). Average HR and %HRmax ((bpm) Z 220 age) was calculated to compare intensity of exercise. HR recovery in the five minutes following each intervention was assessed by determining the mean HR at each minute. Statistical analysis All data are presented as mean SD. Data were normally distributed, assessed using KolmogoroveSmirnov test. Repeated measures analysis of variance (ANOVA) was used to compare: total EE, intervention EE, pre-intervention EE, post-intervention EE, intervention HR and change in HR
Total EE differed between the four conditions (F(3,57) Z 75.0, p < 0.001) (Fig. 2(a)), with calisthenics causing the largest increase (57 16 kcal) compared to all other conditions (Sit: 42 11 kcal, p < 0.001; Stand: 44 12 kcal, p < 0.001; Walk: 52 13 kcal, p < 0.001). Pre-intervention EE was not different between interventions (Stand: 18 5 kcal; Walk: 19 5 kcal; Calisthenics: 19 5 kcal; F(3,57) Z 0.4, p Z 0.8) or sitting (19 5 kcal, p Z 0.8) indicating participants had sufficiently recovered between conditions. Considering the intervention period in isolation (transition 1, intervention period and transition 2) calisthenics resulted in the highest EE (13 5 kcal) (Fig. 2b) compared to sitting (3 1 kcal, p < 0.001) and standing (5 1 kcal, p < 0.001). Recovery EE following the intervention differed between conditions (F(3,57) Z 47.5, p < 0.001) (Fig. 2c) with calisthenics resulting in the highest total EE (27 7 kcal) compared to both walking (23 6 kcal, p < 0.001) and standing (22 6 kcal, p < 0.001). Compared to sitting for 30 min, an additional 6.5% or 3 kilocalories were expended by breaking this period up with 2 min of standing; 24.9% or 10 additional kilocalories were expended walking for 2 min; and 37.8% or 16 additional kilocalories were expended performing 2 min of calisthenics. Larger expenditures would be gained if these interventions were performed over the longer term, assuming energy intake is maintained (Table 1). Exercise intensity All conditions were classified as ‘very light’ intensity (<57 %HRmax) in accordance to the American College of Sports Medicine (ACSM) exercise prescription guidelines [18] (Sit:
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36 6%; Stand: 37 6%; Walk: 43 5%; Calisthenics: 46 6%). Heart rate response The HR response to the intervention differed between conditions (F(3,57) Z 53.5, p < 0.001). Calisthenics (90 12 bpm) and walking (84 10 bpm) HRs were higher compared to sitting (70 12 bpm, both p Z 0.001). Moreover, calisthenics resulted in the highest HR (25 6 bpm) from pre-intervention values compared to walking (17 5 bpm, p < 0.001) and standing (8 5 bpm, p < 0.001). For recovery HR (five minutes following intervention), a significant interaction between condition and time was observed (F(10,150) Z 22.8, p < 0.001) (Fig. 3). Following calisthenics, HR was elevated above baseline at 60 and 120 s into the recovery (p < 0.001), with increases of 12 bpm and 5 bpm respectively. This did not return to near pre-intervention values until 180 s onwards. In contrast following walking, HR remained above baseline for 60 s into the recovery (p < 0.001), with a 4 bpm increase, but returned toward baseline by 120 s. Standing values recovered within the first minute. Discussion
Figure 2 Differences in energy expenditure when completing 30 min sitting (Sit) or breaking up this period with a two minute intervention of: standing stationary (Stand), treadmill walking (Walk) or performing calisthenics exercises (Calisthenics). (2a) Total energy expenditure during the 30 min assessment period. (2b) Energy expenditure during two minutes of sitting and during each two minute intervention. (2c) Energy expenditure during 15 min of sitting and in the 15 min sitting period following each intervention. * Significantly greater than sit (p < 0.001), # significantly greater than stand (p < 0.001), ** significantly greater than walk (p < 0.001). (Error bars Z SD).
This study investigated calisthenics as an alternative intervention choice which could be utilised to interrupt sedentary time. A two minute set of calisthenics as a break during 30 min of sitting, led to a greater total EE and HR response compared to standing or walking for the same time period. Additionally, calisthenics could be performed behind a desk with no additional equipment, increasing the potential practical application in workplaces. Hence, this study presents calisthenics as a potentially more time efficient intervention to break up sedentary behaviour which could be utilised to improve cardiovascular health and weight management. Interrupting sedentary time with calisthenics produced the greatest total EE; higher than standing or walking. The EE for a given activity is determined by the volume of contracting muscle mass [20] and, compared to sitting, standing and walking leads to elevated contractile activity [3,21]. Moreover, quadriceps and hamstring muscle activity is greater when squatting than standing or brisk walking [21]; consequently the muscle activity required to perform the calisthenics would also produce an increased EE. Performing fidgeting-like movements also increases EE compared to remaining motionless [22], demonstrating activating even small musculature can heighten EE. The nature of the calisthenics completed challenged fitness components such as balance and coordination which in turn may have activated a greater number of smaller muscle fibres, such as limb stabilising muscles, as well as larger trunk muscles. It could therefore be possible that this greater overall muscle contractile activity could
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Table 1 Extrapolation of the additional energy expended (compared to sitting) when disrupting 30 min of sitting with 2 min of standing, walking or calisthenics exercises. Time period
1h 8 h working day 5 days of 8 h working days 1 month of 8 h working days 6 months of 8 h working days 12 months of 8 h working days
Energy expenditure (kcal) 2 min of standing once every hour
2 min of walking once every hour
2 min of calisthenics exercises once every hour
3 24 108 432 2592 5184
10 80 412 1648 9888 19,776
16 128 628 2512 15,072 30,144
Note: Once every hour has been selected to best represent a realistic working day, taking into account the possibility of daily events (such as meetings) which may prevent more frequent breaks in sedentary time. Values have been rounded whole numbers.
Figure 3 Mean heart rate at baseline (15 min sitting) and during five minutes of recovery following breaking up this sedentary period with two minutes of: standing stationary (Stand), treadmill walking (Walk) or performing calisthenics exercises (Calisthenics) (shaded area). * indicates calisthenics caused a significantly greater heart rate than baseline (p < 0.001). # indicates walking caused a significantly greater heart rate than baseline (p < 0.001). (Error bars Z SD).
explain the larger EE observed. Additionally, during the recovery following the intervention calisthenics produced a longer elevation of EE and also HR compared to the other conditions. Excess post-exercise oxygen consumption (EPOC) occurs during the recovery following physical activity and a component of this is the increased cardiac response [23]. Consequently, the longer elevation of HR following calisthenics might provide a mechanism to explain the concurrent increased EE observed. Practical applications Using calisthenics as an intervention to break up sedentary time is a more time efficient one than the other methods assessed. Performing calisthenics led to a 37.8% increase (16 kcal) in total EE compared to sitting, whereas walking and standing led to only 24.9% (10 kcal) and 6.5% (3 kcal) increases respectively. Furthermore, previous interventions employed to elevate EE have not achieved such substantial calorific increases. Breaking up sitting desk work with a two minute self-paced walk led to only a 17% increase in EE (8 kcal)
[12]. Only when this intervention was carried out for five minutes did EE nearly match that achieved from the calisthenics in this study, with a 37% increase (17 kcal) observed [12]. Therefore calisthenics can provide the same EE benefits as walking but in less than half the time. Similarly if standing is employed as opposed to sitting, an energy expenditure of 1.37 kcal$min1 [8] has been reported, but this is less than the 1.91 kcal$min1 expended performing calisthenics as an intervention. Moreover, in this study [8] standing was utilised for the entire assessment duration rather than as a break, causing the time length of the meaningful intervention to be considerably longer than a two minute set of calisthenics. In practical terms the time efficiency of calisthenics is of great significance as individuals may lack the opportunity during a workday to spend such considerable time away from their working environment, or may not have access to suitable facilities to stand and work. Calisthenics may also represent a more feasible option to apply to workplaces. The calisthenics routine prescribed overcomes previous limitations, such as equipment costs and workplace restrictions, as it could be easily performed behind a desk, in a small amount of space and with no equipment required. Additionally, based on the HR response, the intensity of the calisthenics routine was only ‘very light’ [18] meaning workers could return to their desk immediately afterwards without feelings of excessive exertion. Longer term benefits Although this was an acute study, the responses observed breaking up sedentary time with a single bout of calisthenics have the potential to produce longer term health benefits if this routine was performed over an extended time period. Employing calisthenics every hour over an eight hour working day, an additional 128 kcal would be expended, well above the daily 100 kcal threshold suggested to reduce weight gain [24]. Extrapolating the EE when walking or standing for a working day, values fail to reach the target 100 kcal a day value [24]. Additionally, potentially larger expenditures could be gained performing calisthenics over an extended time period (Table 1). However, this positive
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Conclusion
change in EE resulting from calisthenics is dependent on whether there is no compensatory increase in energy intake as a result of the increased physical activity [25]. The repeated performance of the calisthenics employed in this study has the potential to maintain or improve additional fitness components such as muscular strength, flexibility and balance, which are specified in current adult physical activity guidelines [17,18]. These core fitness components are essential to everyday functional activities and can deteriorate with age and physical inactivity [26]. It is unknown if longer term cardiovascular or metabolic adaptations could occur performing the calisthenics. The elevation in HR and subsequently blood flow and shear stress has the potential to provide benefits to the vasculature, specifically endothelial function, a measure of cardiovascular health associated with cardiovascular risk [27]. Additionally, the potential of increased muscle mass and subsequent glucose transporter protein content would enhance glucose uptake, improving insulin sensitivity [28].
This study demonstrates calisthenics are a time efficient method to break up sedentary time, which has the practical potential to be employed in workplaces. Calisthenics led to a greater total EE and HR response compared to using standing or walking as an intervention, which in the long term may assist in weight control. This exercise modality also targets fitness components such as muscular strength, balance and co-ordination, which are features of physical activity guidelines. Furthermore, performing calisthenics does not require individuals to leave their desk environment or purchase additional equipment, thus overcoming previous limitations associated with other workplace interventions. Although longer term research is required to assess the feasibility of this intervention, this study presents calisthenics as a promising alternative to break up prolonged workplace sedentary time and improve cardiovascular health and assist in weight maintenance.
Limitations and future research
Acknowledgements
The design of this study was not counterbalanced, therefore it is possible the order of the conditions may have influenced results. To reduce this, a five minute recovery between conditions was included. No differences between conditions in EE or HR prior to each intervention were observed, indicating participants had recovered from the previous condition. The calisthenics intervention utilised only five different calisthenic exercises, selected to target a combination of fitness components. However, utilising different combinations and types of exercises may in turn influence the magnitude of the EE and HR response. Consequently, additional research utilising varied exercises is required. Although performing calisthenics resulted in the highest EE and HR responses, it is acknowledged that following this protocol over an eight hour working day may be too intensive for some individuals. For example over one day an individual repeating this routine would perform 64 repetitions of each exercise, which may be excessive for those without previous experience of these exercise modalities, and this would be further exacerbated over an entire working week. Moreover, this routine utilised only five different types of calisthenics, hence over time their repeated performance could become demotivating, leading to decreased adherence. Additionally, results cannot be generalised to the entire population as the magnitude of change in EE could have been influenced by factors such as body weight [29] and fitness levels [30]. Longer term studies are therefore needed assessing the calisthenics routine over several days to determine the feasibility of individuals carrying out multiple repetitions of the exercises (including changes in work productivity), alongside any potential health complications that may result such as muscle soreness or injury. It may be that a combined approach with walking (or other activities) may be more suitable to interrupt sedentary time. Furthermore this exercise variety could increase adherence, which can be problematic with lifestyle modifications [31].
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